P0204 and P0300 Diagnostic Guide for 2003 VW Jetta 1.8T - Spark Plug & Injector Circuit Issues
I'm experiencing two diagnostic trouble codes on my 2003 Volkswagen Jetta 1.8T: P0204 and P0304. I've already replaced all four spark plugs and ignition coils, but the engine still runs roughly and occasionally stalls when the fourth cylinder engages. Based on my observations, I suspect a faulty spark plug wire that intermittently disconnects or reconnects. I'm not an experienced mechanic, but I'm learning and have a friend who can assist with physical repairs. However, I don't know which parts to replace or how to diagnose this properly. Can anyone offer guidance? Thanks for any advice!
P0204 indicates an electrical circuit fault in the fuel injector circuit, which can often be linked to P0304 (misfire on cylinder 4). I recommend avoiding unnecessary repairs at this stage. A specialized diagnostic tool or software from a certified Euro shop is required to accurately interpret and resolve these codes. Attempting DIY fixes without proper equipment may lead to further issues.